This invention relates generally to an apparatus for applying patches to a moving continuous web, and more particularly to such an apparatus wherein a web of patch material is capable of being cross-perforated, burst into individual patches and transferred on to the moving web all in synchronization with the moving web.
U.S. Pat. No. 3,745,893 discloses an apparatus for applying patches to envelope blanks which are individually transferred to a patch severing and applying station. Adhesive is applied at such station to a web of patch material after which the web is severed and is transferred on to the blanks by means of a vacuum transfer roll.
U.S. Pat. No. 3,468,227 discloses an envelope blank forming machine wherein adhesive is applied to precut envelope blanks, and a web of patch material is severed and applied to the adhesive on the blanks.
U.S. Pat. No. 3,630,124 discloses an apparatus for applying window patches to precut envelope blanks wherein a web of patch material has adhesive applied thereto, is subsequently partially severed and is advanced over a transfer roll where bursting takes place as spaced fingers engage successive patches to complete the severing thereof. The individual patches are then transferred on to the precut envelope blanks.
Difficulties arise in controlling the transfer of the individual patches on to the precut blanks, especially at high operating speeds, when using those prior art machines wherein the web of patch material is completely severed into individual patches (the '893 and the '227 patents) as well as with the use of the machine disclosed in the '124 patent wherein the web of patch material is partially severed and subsequently burst into individual patches. Besides, the synchronization between the moving precut blanks and the cutting, bursting (where applied) and transferring of the patches thereto is difficult to maintain in these prior art arrangements.